Monday, January 17, 2011

I've finally got it under control

It looks like I've finally got the timing and EMF noise issues under control. This mostly involved moving the firing logic into a computer instead of a single-purpose circuit and putting in shielding.

In the long run adding the computer will mean less wiring as the computer can handle a number of the firing circuits. In the short run, it means the circuits I've been making are a waste. I can use them for the first few stages but as more precision is needed later they can't do the job.

You can see from the graph that as I change the delay (x-axis) I can get a fall in the time between speed measuring gates (y-axis). The fact that this relationship exists implies that I'm actually adding power to the munition again and ass I add and tune more magnets in the future that munition will actually go faster.

On the plus side, when looking at this graph it's clear that the region-of-good-performance is quite wide. The numbers correspond to at least 300us of delay from one end of that region to the other (and it may even be as wide at 600us). At the speed of 50m/s our 4cm round is passing a location in 800us. If we essentially don't care about the position of that round for 300us of that 800us, we're really only using 500us for acceleration. At 4cm in length, this means we should be able to hit 4cm/500us = 80m/s before we see degradation in the performance of each magnet. At the optimistic max of 600us, we could see 200m/s before we begin to see that loss of efficiency.

Next step: Getting this prototype magnet controller to scale up to 13 of them.